A significant problem in using today's digital watches is their complexity. A recent article in The Atlantic Monthly ("The Complexity Problem", March, 1993, p. 96) reported that a line of advanced digital watches produced by a manufacturer "was being returned as defective by the thousands, even though the watches actually worked perfectly well." The returns were made either soon after purchase or "thereafter in two large batches--in the spring and the fall, when the time changed", with the primary problem the difficulty of user's being able to reset such a complex watch.
The essential problem with control of a digital watch is that there is little space available for buttons and keys, and designers have found it necessary to device procedures in which a small number of keys are pressed into service to perform increasingly complex functions. Typically, this is done by using one or more buttons that, when pressed, moves the watch sequentially through a set of modes. Thus, for example, the watch may begin in a normal time display mode and then, after a single press of the mode button, change to "alarm" mode, which displays and allows resetting of the time and dates for an alarm. A second press of the mode button might display the time in multiple time zones, a third make available a "Countdown alarm", and a fourth provides a stopwatch, with the fifth press returning the watch to its normal time display mode.
Similarly, the pressing of a different mode button might place the watch into a special mode for setting the time. The pressing of the first button might then shift the watch into a sequence of specific modes for setting the watch, with each mode allowing the setting of seconds, hours, minutes, month, date, and year, with successive presses.
Within each mode other buttons are used for particular functions. For example, in the timesetting function a particular button might, when pressed, advance the "minutes" parameter from "45" to "46". However, typically, there is not button allowing a decrementing of the value, and users are often frustrated by having to cycle through all of the values from 46 to 59, then 0, and again to 45, for example. While most watches now have a function in which holding down the button for a period of time causes repetitive advancing, without the user having to continually repeat the step of pressing the button, people often miss stopping at the correct time and must cycle through again. In general, the "mode" orientation of the user interface of conventional digital watches and the tendency to force many functions into a small number of buttons results in the function of most buttons being highly context dependent, with no obvious metaphor or model for the user to follow to remember a button's function in a particular context.
Given that watches today are so accurate that setting is done very infrequently (for many users only twice a year when changing from standard to daylight time and back again), users typically retain little skill in the task and frequently misplace their instruction manuals some time after purchase of the watch, and often find such manuals very difficult to understand. The net result of this is a high degree of frustration and an inability to correctly use the watch for many users.
As digital watches become more complex they are becoming increasingly difficult to use, and it is probably fair to say that the primary obstacle to the further development of value and functionality in a digital watch may soon be, if it is not already, the limits posed by the cognitive complexity of the watch, rather than the ability to economically and compactly manufacture additional computing and display functions.
Another limitation on the inclusion of additional functions into watches is the unwieldy number of keys that are required for use of these functions. Such functions as calculators and data storage and retrieval systems (used, for example, for names and telephone numbers) typically require not only control functions but a relatively large set of input values (e.g., the digits 0-9 and operators in the case of a calculator, the digits 0-9 and letters A-Z for data retrieval systems). Conventional watches that contain these functions are typically provided with a substantial number of keys to allow their operation. For example, the Casio World Time Databank Calculator has 16 keys and 4 buttons. Of the 16 keys, 13 have 3 functions--a given press can mean one of two different letters or a digit, depending upon the context. The size of such keys is generally so small that users typically make large numbers of errors in pressing the keys. Another recently introduced watch of considerable utility results from combining a watch with a miniature remote control for televisions and videocassette recorders. However, the number and size of the keys required to be added to the watch to allow this function is a major disadvantage.
In some watches a display with a "menu" of functions that can be selected is provided, including the DBX-100 Databank Watch manufactured by Casio Computer Corp. and and the Windsurfer watch manufactured by Citizen Watch Company. In both cases, a menu of potential selections is displayed, with the selected option indicated. Repeated pressing of a button results in changing the selection. The Moriya invention (U.S. Pat. No. 4,115,993) describes a digital alarm watch in which manual switches select one of a set of channels of alarm times, with the particular channel selected displayed, and with manual switches capable of resetting the alarm time. The Planzo invention (U.S. Pat. No. 4,354,260) describes a personal data storage and retrieval system that is part of a digital watch. Digits and letters are entered by the user by initiating an action in which a set of digits or letters are displayed sequentially, one by one, with the user pressing a button to enter the letter that was most recently presented. The Hatuse, et al invention (U.S. Pat. No. 4,257,115) is a watch with a touch sensitive area surrounding each number on the display of an analog clock face. Pressing the area around the numerals 1-9 enters the corresponding digit, while pressing "10" enters the digit 0, and pressing "11" and "12" enters control functions.
In addition, the Sheff invention (U.S. Pat. No. 5,088,070) describes a menu-based interface in which choices are made from a matrix of rows and columns on a display. The basic input device is a set of four buttons arranged like the points of a compass, with each button, if pressed, resulting in movement up, left, down, or right of a designation that marks a choice, such as turning on a marker near a menu choice. A fifth button, in the center of the other four, actually chooses the selection when pressed. A variation provides a hemisphere such that pressing down the hemisphere in one of the four directions can result in closing a switch that has the same effect as if one of the four buttons was pressed, and pressing the sphere directly downward has the stone effect as pressing the central button.
The above approaches typically require multiple presses of buttons or similar actions, and typically either are so small that they are difficult to operate or are too large to fit easily in the usual watch configuration (which is generally flat). What is needed is an approach in which a small number of input devices is used, with some property of the device (such as amount, direction, and speed of movement) capability of encoding much more information than is the on-off switches used in the above inventions, and in which the device has a shape and motion that is compatible with the physical requirements of the typical watch.